Relativistic Heavy Ion Collider

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Relativistic Heavy Ion Collider
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Quarks and Gluons

• Quarks and gluons are the constituents of protons
  neutrons, atomic nuclei, neutron stars
  (pulsars), and the very early universe.
• A proton has three quarks (uud) plus a
  fluctuating cloud of quark anti-quark pairs and
  gluons.
• E mc2. In energy units, the mass of the proton
  is 938 MeV/c2.
• The 3 bare quarks of the proton contribute only
  15 MeV/c2 to the mass of the proton.
• One of the central goals of particle physics is
  to find the origin of this 1.5 of the mass of
  the proton.
• The central goal of Jefferson Lab, and the
  Relativistic Heavy Ion Collider is to understand
  the origin of the other 98.5 of the mass of the
  proton.
• This is also 98.5 of the mass of the visible
  matter of the universe.

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Quark and Gluon waves

• Any wave is described by its wavelength l and
  frequency f1/T.
• Energy density carried by a wave is proportional
  to amplitude squared.
• Quantum waves
• Momentum l / h
• Energy f h
• Relativity Emc2 (p0)
• E2 (pc)2 (mc2)2

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Quark and gluon waves interact by creation and
annihilation

• Quark wave ? Quark Gluon waves
• Anti-Quark wave ? Anti-Quark Gluon waves
• QuarkAnti-Quark ? Gluon wave
• Gluon wave ? Quark Anti-Quark waves
• l1 l2 l3
• f1 f2 f3
• These conditions violate the mass constraint E2
  - (pc)2 (mc2)2
• Quarks gluons almost massless.
• The Off-mass-shell waves only propagate for a
  time h/(E-pc)

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The Jefferson Lab Strategy

• Focus the simplest systems
• Protons, Deuterons, Helium,
• Study with a well understood microscope
• Short wavelength Photon and Electron waves
• Study at short distance inside the proton,
• QCD (better) understood.

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The Relativistic Heavy Ion Collider (RHIC)
strategy

• Symmetric Au-Au collisions at high energy
• Total energy 2A200 GeV, A 197 nucleons
• Apply Thermodynamics to nuclear matter at high
  temperature
• Recreate the conditions of the early universe
• Look for phase transitions between hadronic
  matter (protons, neutrons, pions) and
  Quark-Gluon Plasma.

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Create a little bang in the lab!
Use accelerators to reach highest energy vBEAM
0.99995 x speed of light at RHIC center of mass
energy ?s 200 GeV/nucleon Use heaviest beams
possible maximum volume of plasma 10,000 quarks
gluon in fireball
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RHIC at Brookhaven National Laboratory
RHIC is first dedicated heavy ion collider 10
times the energy previously available!
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4 complementary experiments
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Black Body Radiation
Radiated Power

• Peak frequency proportional to Temperature
• fpeak 2.82 kT/ h
• Total power radiated per unit area

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Cosmic Microwave BackgroundNASA/WMAP Science
Team
Red to Blue, T 2.725?0.001 K
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Black Body Radiation from Relativistic Heavy Ion
collisions

• At low temperature, neutrons and protons are
  boiled out of the nuclei
• If kT gt mc2, particles are created (mostly pions,
  mc2 140 MeV).
• The Black Body radiation depends upon the number
  of degrees of freedom
• Low temperature 2 x 2 (protonneutron) x spin
• High temperature (3 x 3 8)x 2 3 quark flavors
  times 3 quark colors times 8 gluon color
  anti-color states.

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In AA QCD in non-perturbative regime
Lattice
e Energy density
T/Tc
Physics is soft Lattice QCD says Create these
conditions to look for new physics
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Is the energy density high enough?
PRL87, 052301 (2001)
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history of heavy ion collisions
high e, pressure builds up
g, g? ee-, mm-
p, K, p, n, f, L, D, X, W, d,
Real and virtual photons from q scattering
sensitive to the early stages. Probe also with q
and g produced early, passing through the
medium on their way out.
Hadrons reflect medium properties when inelastic
collisions stop (chemical freeze-out).
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Particle production (lots!)
sum particles under the curve, find 5000
charged particles in collision final state (6200
in 200 A GeV central AuAu)
In initial volume Vnucleus Rescattering should
be important!
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Measuring Impact Parameter

• On an event-event basis, collisions are highly
  localized (but random).
• Multiplicity of particles in a set of reference
  detectors is a good surrogate for impact
  parameter

• Higher multiplicity for central collisions
• Sharp cutoff for grazing collisions.
• Extreme forward detectors measure low
  multiplicity for central collisions.

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More evidence for equilibrated final state
Observed hadron ratios in agreement with thermal
ratios! T(chemical freeze-out) 175 MeV
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Early state? a barometer called elliptic flow
Origin spatial anisotropy of the system when
created, followed by multiple scattering of
particles in the evolving system spatial
anisotropy ? momentum anisotropy
v2 2nd harmonic Fourier coefficient in
azimuthal distribution of particles with respect
to the reaction plane
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a unique probe for physics of hot medium
Probe Jets from hard scattered quarks Observed
via fast leading particles or azimuthal
correlations between the leading particles

• But, before they create jets, the scattered
  quarks radiate energy ( GeV/fm) in the colored
  medium
• decreases their momentum (fewer high pT
  particles)
• kills jet partner on other side
• jet quenching

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Au-Au ?s 200 GeV high pT suppression!
nucl-ex/0304022
Au-Au nucl-ex/0304022
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jet correlations AuAu vs pp
STAR PRL 90, 082302 (2003)
Peripheral Au Au
Central Au Au
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Experiments show NO suppression in dAu!
PHENIX Preliminary p0
STAR Preliminary
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?0 RAA vs. predictions
Theoretical predictions dAu I. Vitev,
nucl-th/0302002 and private communication.
AuAu I. Vitev and M. Gyulassy, hep-ph/0208108,
to appear in Nucl. Phys. A M. Gyulassy, P. Levai
and I. Vitev, Nucl. Phys. B 594, p. 371 (2001).
Initial state mult. scatt.,shadowing final
state dE/dx (AuAu) Also Kopeliovich, et al
(PRL88, 232303,2002) predict RpA1.1 max at
pT2.5 GeV projectile as color dipole
anti-shadowing
shadowing
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Conclusions

• Huge multiplicity of particles in each event
  allows approach to statistical (thermodynamic)
  treatment
• Many ideas are semi-classical.
• Extreme energetic particles, heavy particle
  (charm) probe interior of expanding fireball.
• Correlations in multiparticle emission allow more
  detailed image of events.
• Theory is mostly crude, but trying to understand
  essential dynamics.

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Centrality Dependence
Au Au Experiment
d Au Control

• Dramatically different and opposite centrality
  evolution of AuAu experiment from dAu control.
• Jet Suppression is clearly a final state effect.